1. Technical Field
The disclosure relates to an ink circulation type inkjet printer.
2. Related Art
Japanese Unexamined Patent Application Publication No. 2008-162262 describes an ink circulation type inkjet printer that performs printing by ejecting ink from an inkjet head while circulating the ink.
In some ink circulation type inkjet printers, ink is circulated by an air pump applying a positive pressure and a negative pressure to a positive pressure tank and a negative pressure tank, respectively, the positive pressure tank being disposed upstream of the inkjet head, the negative pressure tank being disposed downstream of the inkjet head.
When such an inkjet printer performs printing, the air pump applies a positive pressure and a negative pressure respectively to the positive pressure tank and the negative pressure tank, both of which are set in a sealed state Thus, the ink flows from the positive pressure tank to the inkjet head. The ink, which is not consumed by the inkjet head, is collected by the negative pressure tank. Also, the ink is delivered from the negative pressure tank to the positive pressure tank by an ink pump according to the liquid level heights in the positive pressure tank and the negative pressure tank. In this manner, the ink is circulated.
During the circulation of ink, the pressures in the ink tanks (the positive pressure tank, the negative pressure tank) are regulated in order to ensure a circulation flow rate (flow volume) and to maintain a nozzle pressure of the inkjet head at an appropriate value. The pressures are regulated, for instance, by driving the air pump and opening/closing a pressure regulation valve.